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THEORY AND METHODS OF NATURAL HAZARDS RESEARCH
UDC: 912:551.053:007(498) DOI: 10.2298/IJGI1303073I
MAPPING SOIL EROSION SUSCEPTIBILITY USING GIS
TECHNIQUES WITHIN THE DANUBE FLOODPLAIN, THE CALAFAT - TURNU
MĂGURELE SECTOR (ROMANIA)
Oana Ionuş*, Sandu Boengiu1*, Mihaela Licurici*, Liliana
Popescu*, Daniel Simulescu* *University of Craiova, Romania –
Geography Department Received 02 August 2013; reviewed 20 September
2013; accepted 01 October 2013 Abstract: The Danube floodplain, the
Calafat – Turnu Măgurele sector, through its main features
(topographic and climatic characteristics, land use and soil type)
and human activities, constitutes an area exposed to soil erosion.
The main objective of the present research is to map soil erosion
susceptibility using the GIS techniques for the computation and
representation of areas, which are exposed to soil erosion
correlated with the field data for the validation. Analyzing the
entire model, the relatively simple methodology, the database
consistence, the comparability of the results with the existent
soil erosion values at national and local scale, we can say that
the model was applied with success in the studied area (areas and
classes of water erosion susceptibility: very low, low, moderate,
high - Ciupercenii Noi, Desa, Măceşu de Jos, Grojdibodu, Orlea,
very high - Rast, Negoi, Catane, Bistreţ, Goicea; areas and classes
of wind erosion susceptibility: very low, low, moderate -
Ciupercenii Noi, Dăbuleni, Ianca, high - Calafat, Poiana Mare,
Desa, Goicea, Piscu Vechi, very high - Poiana Mare, Rast, Negoi,
Bistreţ, Gighera, Orlea. The soil erosion susceptibility map can be
useful for planning erosion control measures and for selecting
suitable sites for runoff plot experiments.
Keywords: the Danube floodplain, soil, water erosion, wind
erosion, database, GIS analysis, susceptibility
Introduction
In the context of environmental protection, most concerns about
erosion are related to accelerated erosion, where the natural rate
has been significantly increased mostly by human activity.
Soil erosion is one of the most critical environmental hazards
of modern times. Simple methods such as the universal soil loss
equation (USLE) (Wischmeier and Smith 1965, 1978), the modified
universal soil loss equation (MUSLE) (Wiliams 1975), or the revised
universal soil loss equation (RUSLE) (Renard et
1 Corresponding author: [email protected]
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al. 1997) are frequently used for the estimation of soil erosion
from watershed areas.
There are several possible methodologies for creating an erosion
map of Europe, some of which are reviewed by Gobin et al. (2002)
and Grimm et al. (2001). Some of these are based on the collection
of distributed field observations, others on an assessment of
factors, and combinations of factors, which influence erosion
rates, and others primarily on a modeling approach. All of these
methods require calibration and validation, although the type of
validation needed is different for each category.
The studied area is located in the south-western part of
Romania, on a distance of about 200 fluvial kilometers, between the
town of Calafat and the town of Turnu-Măgurele, covering an area of
ca. 200,000 hectares (of which 95,000 hectares represent the
floodplain proper) (Licurici et al., 2013).
In the context of the general diversion tendency towards the
right, imposed by the neotectonics of the region and by the
morpho-climatic stability, during the Holocene, the Danube induced
the withdrawal of the right slope of the Prebalkan Tableland and
within this space there resulted the present river floodplain,
significantly more developed on the left side and being dominated
by the relatively high slope of the morphological unit across the
Danube (Fig. 1). Under the name of the Danube Floodplain there is
to be understood all that the Danube built through alleviation and
which undergoes the direct action (in natural regime) of the river
(***, Geografia Văii Dunării româneşti, 1969). Locally, there
appear significant changes because of the increased supply of
alluvia and because of the sand dunes or alluvial fans.
Fig. 1 The Danube Floodplain within the Calafat-Vidin - Turnu
Măgurele-Nikopole sector.
Hypsometry
The minor landforms of the floodplain proper are rather
heterogeneous and their organization sometimes forms genuine
geographical individualities. However, in
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general terms, there is to be noticed a succession of
longitudinal stripes: the sandbank located near the riverbed (often
the higher area), the middle floodplain (partially swampy), and the
low depressions that formerly represented extensive water bodies
(lakes, ponds, marshes). Often, the complexity of the relief is
augmented by the presence of sand dunes (which sometimes cover the
geomorphologic contact) (Calafat – Desa – Pisculeţ, Călăraşi -
Dăbuleni etc.) or of the erosion steep. Conclusively, on the sector
analyzed in the present paper, the altitudes descend from the
Danube towards the interior and up to the central part of the
floodplain or even to the neighbouring terrace. The values of the
relative altitude are comprised between less than 20 and 40
meters.
With more than half of the population leaving in rural
settlements, the area under study greatly depends on agriculture,
which is commonly the most vulnerable economic sector to natural
hazards (Benson and Clay, 2004). Within the analysed area, arable
land prevails, with more than 130,000 hectares (Fig. 2), accounting
for 85% of the total agricultural terrains; hayfields and pastures
cover almost 18,000 hectares (12%), permanent crops representing
just 3% (3823 ha) of the total agricultural terrains. Some of the
communes own large surfaces of arable land, as it is the case with
Poiana Mare (8259 ha), Bistreț, Gighera, Călărași, Gura Padinii
(more than 7000 ha). Poiana Mare and Bistreț also have large
heyfields and pastures (1400-1700 ha), while Ghidici, or Măceșu de
Jos have less than 200 ha.
Fig.2 Land cover map within the Danube floodplain. Calafat-Turnu
Măgurele sector
(Source: Corine Land Cover, 2006, EEA)
Soils within the Danube floodplain are moderately developed,
being influenced directly by the new material deposited during the
floods on the low terraces and
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by the aquifer lying at low depth (alluviosols, glycols,
psamosols and loose sands) (Fig. 3):
– in the areas where the aquifer is mineralized and hydric
regime favours the salinization process (Gighera, Ostroveni, Bechet
and Potelu precincts),salic alluviosols appear (Photo.1).
– in the case of the gleyic alluvisols, the aquifer is found at
depths varying on average between 1 and 2 metres, while during the
rainy periods, when the water flow on the rivers increases, it can
be found near the surface (in patches southwards of Gârcov and
Izlaz).
– between Ciupercenii Noi, Desa and Zăval, typically gleyic
chernozems cover larger areas (Photo.2). The aquifer is found at a
low depth (2-3 m); consequently, there is a moderate gleyzation
process.
Photo.1 Soil degradation by hydro-climatic
variations, south of Bistreţ (Licurici et al., 2013)
Photo.2 Soil erosion on sands with clay
intercalations, south of Zăval) (Licurici et al., 2013)
– at Poiana Mare-Ciupercenii Noi-Desa area and north of Bechet
and Giuvărăşti, where the aquifer is at a lower depth, Patches of
cambic, wet-phreatic chernozems are found.
– erodic anthrosols are very to excessively eroded or uncovered
soils, and the remaining horizons do not allow their classification
in a particular type of soil. Within the study are, they cover very
small areas, north of Calafat, having a sandy, loamy or
loamy-clayish texture.
– for the Ciupercenii Noi-Desa-Ghidici area, as well as
southwards of Bistreţ, Cârna and Gighera, having a sandy texture,
the loose sands are specific. Loose sands in association with
psamosoils and gleyic chernozems, on sands, are found on the lower
terraces of the Danube,
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south of Ciupercenii Noi-Desa_Piscu Vechi, Bistreţ-Cârna-Gighera
and within Potelu precincts. There is a strong gleyzation due to
the aquifer situated at very low depth.
– psamosoils were formed on parental material made up of sandy
aeolian deposits, under a vegetation of xerophytes herbaceous
sandy. They are found southwards of Ciupercenii Noi-Desa-Piscu
Vechi-Ghidici, Cârna-Măceşu de Jos-Gighera,
Ostroveni-Bechet-Călăraşi-Ianca. Locally, they are associated with
loose sands.
– in the depression-like areas within the floodplains and
plains, Gleysols are found. They are formed on varied deposits from
the texture point of view, such as fluvial, fluvial-limnic, limnic,
sands etc. and their genesis is conditioned by the presence of the
aquifer at low depth.
Legend: ASen = Enthic alluvisols, ASen, gleyic = Enthic gleyic
alluvisols, ASeu or ka = Eutric with calcaric alluvisols, ASgc =
Gleyic alluvisols, ASsc = Salic alluvisols, ATer = Erodic
anthrosols, CZcb = Cambic chernozems, CZcb and Czti, gleyic =
Cambic, gleyic chernozems in association with typical, gleyic
chernozems, CZcb, Fzar = Cambic chernozems associated with argic
phaeozems, CZcb, wet-phreatic = Cambic, wet-phreatic chernozems,
CZcb, on sands = Cambic chernozems on sands, CZcb, vermic = Cambic,
vermic chernozems, CZcb-erod = Cambic, eroded chernozems, CZgc-al =
Alluvic-gleyic chernozems, CZgc-al-ss = Salsodic alluvic gleyic
chernozems, CZgc-ss = Gleyic–salsodic chernozems, CZka,
wet-phreatic = Calcaric, wet-phreatic chernozems, CZka,vermic =
Calcaric, vermic chernozems, CZti = Typical chernozems, CZti,
eroded = Typically eroded chernozems, CZti, wet-phreatic = Typical,
wet-phreatic chernozems, CZti, gleyic = Typically gleyic
chernozems, GS = Gleysols, Lakes and waterbodies, Swamps, Loose
sands, Loose sands 1 = Loose sands in association with psamosoils
and cambic chernozems, Loose sands 2 = Loose sands in association
with psamosoils and gleyic chernozems, on sands, PS = Psamosoils,
PS, loose sands = Psamosoils in association with loose sands, SNal
= Alluvic solonetzs, SNti, SNlv = Typical solonetzs in association
with alluvic solonetzs
Fig.3 Soil map of the Danube Floodplain, Calafat-Turnu Măgurele
sector (Source: Romanian Soil Classification System data updating
to the new Romanian Soil Taxonomy
System, 2012)
Geomorphic hazards related to soil degradation are also to be
put in connection with the inadequate agricultural techniques,
deforestation, overgrazing, interruption of the lateral connection
between floodplain and the Danube etc. Geomorphic hazards primarily
related to (rain) water erosion concern any slope
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area within the floodplain and the geomorphologic contact of the
floodplain with the high terrace (Licurici et al., 2013).
Geomorphic hazards primarily related to wind erosion concern
deflation, abrasion and deposition of the sand. Large surfaces of
the floodplain (Calafat – Ciupercenii Noi – Desa – Piscu Vechi –
Ghidici, Bechet – Dăbuleni etc.) are vulnerable to this type of
hazard, which is to be assessed in the context of the land use/land
cover changes (cutting down of forest shelter-belts, deforestation,
removal of the natural vegetation, usage of pesticides, which
leaves the soil naked between crops etc.) and climatic changes
(long dry/drought periods, increased occurrence of storms,
high-speed winds etc.) (Licurici et al., 2013).
Data and methods
Because the GIS is an efficient tool for managing spatial data
and suitable for soil erosion calculations, there have been
published various studies of soil erosion using GIS (Mitasova et
al. 1996, 1998). The large number of variables taken into
consideration in determining the susceptibility as well as the
complexity of the model require several characteristic steps to be
performed. The outcome of this study, the soil erosion
susceptibility map, was achieved through a multiple spatial overlay
analysis. This analysis was performed with the ESRI ArcGIS
geoinformation software, analysis module “Spatial analyst”, the
Raster Calculator function that makes possible the integration of
mathematic equations into GIS (Bilaşco et al. 2009).
In the implementation process of the soil erosion susceptibility
model, we created a vector and raster GIS database covering the
studied area, using specific spatial analysis methods and database
interrogations. Considering the necessities of the susceptibility
map, a GIS database complexly structured on vector and raster
layers was created, starting from the primary database (contours,
hydrography, soil and land cover) to the derivate data (digital
elevation model) and finishing with the modeled database, raster
structures (water and wind erosion grid and soil erosion
susceptibility grid) (Tab. 1). The grid format offers many
advantages due to the simplicity of operation through matrix
algebra, and has been used by many researchers in heuristic or
statistical analysis.
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Table 1 Database structure used in soil erosion susceptibility
map Name Type Structure Attribute Origin
Contour vector line altitude primary Hydrography vector line
name, order, direction primary
Soil vector poligon type, texture primary Land cover vector
poligon category of use primary
DEM raster grid altitude derivate water soil erosion raster grid
soil erodibility factor modelled
wind soil erosion raster grid soil erodibility factor
modelled
soil erosion raster grid soil erosion susceptibility
modelled
Results and discussions
A comprehensive assessment of soil erosion and the development
of erosion-control plans in any area requires consideration of both
wind and water erosion.
Water erosion includes the processes of detachment, entrainment,
transport, and deposition of soil particles caused by raindrop
impact and surface runoff over the land surface. Soil properties
determine its inherent erodibility (susceptibility) to erosion.
Wind erosion causes soil-texture changes because fine particles are
removed, decreases soil depth and fertility and decreases land
productivity.
To the soil database (Romanian Soil Classification System
updating to the new Romanian Soil Taxonomy System, 2012), the soil
erodibility coefficient dependent to the soil type and texture was
introduced as attribute. Their value vary between 1 and 5. The
resulted values were grouped into five classes corresponding to a
particular susceptibility: very low, low, moderate, high and very
high.
Within the Danube Floodplain, Calafat-Turnu Măgurele sector the
areas characterized by: water erosion correspond to the following
classes of susceptibility (Fig. 4): very low, low, moderate, high
(Ciupercenii Noi, Desa, Măceşu de Jos, Grojdibodu, Orlea), very
high (Rast, Negoi, Catane, Bistreţ, Goicea); wind erosion
correspond to the following classes of susceptibility (Fig. 5):
very low, low, moderate (Ciupercenii Noi, Dăbuleni, Ianca), high
(Calafat, Poiana Mare, Desa, Goicea, Piscu Vechi), very high
(Poiana Mare, Rast, Negoi, Bistreţ, Gighera, Orlea).
The spatial analysis module “Spatial Analyst”, with the Raster
Calculator function permits the integration of mathematic equations
in GIS environment.
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Therefore, regarding the soil erosion susceptibility map we
converted the two database – water erosion and soil erosion (grid
type) by interrogating the attributes representing the
susceptibility.
The evaluation model is based on quantitative classification and
five classes of susceptibility (Fig. 6) are derived by comparing
tolerated and computed erosion values (water erosion and wind
erosion): very low, low, moderate, high and very high. Analyzing
the resulting maps of the soil susceptibility we identify the areas
with very high and high susceptibility (Rast, Negoi, Bistreţ,
Măceşu de Jos and Grojdibodu). Within the Danube Floodplain,
Calafat-Turnu Măgurele sector areas affected by soil erosion are
generated by the the aquifer situated at very low depth and by the
the soils texture (fluvial, fluvial-limnic, limnic, sands etc)
mostly extended in the Dolj county.
The model validation was achieved by field trips meant to
identify by direct observation or by using a GPS in some areas
affected by soil erosion then we compared the results with the
modeled database.
Fig. 4 Water erosion susceptibility of the Danube Floodplain,
Calafat-Turnu Măgurele sector
Fig. 5 Wind erosion susceptibility of the Danube Floodplain,
Calafat-Turnu Măgurele sector
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Fig. 6 Soil erosion susceptibility of the Danube Floodplain,
Calafat-Turnu Măgurele sector
Conclusions
The complexity of the GIS spatial analysis model presented in
this study, the results’ accuracy and its good validation prove its
significant utility for the practical research in the field and
supports its extrapolation to other territories.
The application of a process model for the soil erosion
susceptibility map has been preferred here for three main
reasons:
1. it applies the same objective criteria to all areas within
the Danube floodplain, Calafat-Turnu Măgurele sector, and so can be
applied throughout the Bulgarian side, subject to the availability
of suitable generic data;
2. it correlates more inputs by using GIS for resulting the
susceptibility classes and their distribution in the analyzed
area;
3. the methodology can be re-applied with equal consistency with
improved current data, and for scenarios of changed climate and
land use.
The soil erosion susceptibility classes can be useful for
planning erosion control measures given that the environmental
legislation, regulations, and certification focus societal
attention on short- and long-term impacts of soil erosion and
sedimentation.
Acknowledgements We kindly acknowledge the county and regional
institutions that supplied important information from their
statistical database (branches of the National Statistics
Institute). The research was supported by the Cross Border
Cooperation Romania-Bulgaria Programme 2007-2013, in the framework
of the project Romanian – Bulgarian Cross-Border Joint Natural and
Technological Hazards Assessment in the Danube Floodplain. The
Calafat-Vidin - Turnu Măgurele-Nikopole Sector (ROBUHAZ-DUN), MIS
ETC Code 350 and project number 2(4.i)-2.2-5.
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References
Bilaşco Şt., Horvath C., Cocean P., Sorocovschi V, Oncu M.
(2009). Implementation of the USLE model using GIS techniques. Case
study the Someşean Plateau. Carpathian Journal of Earth and
Evnironmental Sciences, .4, (2), 123-132.
Gobin, A., Govers, G., Jones, R.J.A., Kirkby, M.J., Kosmas, C.
(2002). Assessment and reporting on soil erosion: Background and
workshop report. EEA Technical Report, 84, 131. Copenhagen.
Grimm, Mirco, Jones, Robert J.A., Montanarella, Luca. (2001).
Soil Erosion Risk in Europe. EUR 19939 EN. Office for Official
Publications of the European Communities, Luxembourg, 40.
Licurici M., Ionuş O., Popescu L., Boengiu S. (2013). Typology
of hazards within the Danube Floodplain, the Calafat – Turnu
Măgurele sector. In Oltenia. Studii şi comunicări. Ştiinţele
Naturii, Oltenia Museum. Craiova – in press.
Mitasova H., Hofierka J., Zlocha M., Iverson L. R. (1996).
Modeling topographic potential for erosion and deposition using
GIS. Int. Journal of Geographical Information Science, 10(5),
629-641.
Mitasova H., Mitas L., Brown W.M., Johnston, D. (1998).
Multidimensional Soil erosion/deposition modeling and visualization
using GIS, Final report for USA CERL. University of Illinois,
Urbana-Champaign. p.24.
Renard K. G., Foster G. R., Weesies G.A., McCool D. K., Yoder D.
C. (1997). Predicting Soil Erosion by Water – A Guide to
Conservation Planning with the Revised Universal Soil Loss Equation
(RUSLE). U.S. Dept. of Agric., Agr. Handbook No. 703.
Williams, J. R. (1975). Sediment – yield prediction with
universal equation using runoff energy factor. Proceedings of the
sediment- Yield Workshop, USDA Sedimentation Laboratory, Oxford,
Mississippi.
Wischemeier W. H., Smith D. D. (1965). Predicting
rainfall-erosion looses from Cropland East of the Rocky Mountains.
Guide for selection practices for soil land water conservations, US
Department of Agriculture in cooperation with Purdue Agricultural
Experiment Station, Agriculture Handbook 282, 47.
Wischemeier W. H., Smith D. D. (1978). Predicting rain fall
erosion losses - a guide to conservation planning, Department of
agriculture, Handbook No.537, US Dept Agric., Washington, DC., p.
63.
*** (1969), Geografia văii Dunării româneşti, the Printing House
of the Romanian Academy, Bucureşti.
*** The ESRI Guide to GIS Analysis, Vol. 1, 1999, Geographic
Patterns and Relationships, ERSI Press, Redlands, USA, p 186.
*** CORINE (2006), Soil Erosion Risk and Important Land
Resources in The Southern Regions of the European Community,. EUR
13233, Luxembourg, p. 34.
*** Romanian Soil Classification System data updating to the new
Romanian Soil Taxonomy System, 2012.